Apparatus for accreting molten copper on a moving core member

ABSTRACT

This patent relates to an improvement in the apparatus for a continuous casting dip-forming process. In the dip-forming process for making wire rod a core member is passed upwardly through a crucible containing a molten metal. The crucible contains a nozzle or bushing through which the core member passes at a relatively high rate. Construction materials for this nozzle or bushing element are critical in obtaining high-quality wire rod.

United States Patent Inventors Marblehead;

Italo S. Servi, Lexington; Chihchung Wang, Lexington, all of Mass.

Appl. No. Filed Patented Assignee 25,770 Apr. 6, 1970 Oct. 5, 1971 New York, N.Y.

Donald A. Corrigan Kennecott Copper Corporation APPARATUS FOR ACCRETING MOLTEN COPPER ON A MOVING CORE MEMBER 2 Claims, 4 Drawing Figs.

US. Cl

lnt. Cl

Field of Search l9, 404,405,4l9,420, 125, DIG. 18; 117/114, 131; 164/86; 75/175 R, 176

75/176 B056 3 12 ll8/DlG.

- [56] References Cited UNITED STATES PATENTS 3,091,217 5/1963 Seymour 1 18/420 3,160,517 12/1964 Jenkin 118/495 X 3,227,577 1/1966 Baessler et al. 118/420 X 3,354,864 11 1967 Knapp 118/63 3,424,130 1/1969 Byrnes et a1. 118/405 Primary Examiner-Morris Kaplan Attorney-John L. Sniado ABSTRACT: This patent relates to an improvement in the apparatus for a continuous casting dip-forming process. In the dip-forming process for making wire rod a core member is passed upwardly through a crucible containing a molten metal. The crucible contains a nozzle or bushing through which the core member passes at a relatively high rate. Construction materials for this nozzle or bushing element are critical in obtaining high-quality wire rod.

PATENTEDum SIB?! 3 10 204 sum 1 OF 2 @g le 2? g /29 Q |9 ,fla l 24/ I2 vl p II 2/ g}: 1 I o (6) O FIGURE INVENTORS DONALD A. CORRIGAN ITALO S. SERVI C. C. WANG BYOZOMMM m ATTORNEY PATENTED GET 5 I971 3,610,204

' FIGURE 2A araccvlpl FIGURE 28 A INVENTORS m DONALD A. CORRIGAN 6| ITALO s. SERVI .1211. c. c. WANG E 65 67 ofinfl/l Mm FIGURE 2C ATTORNEY APPARATUS FOR ACCRETING MOLTEN COPPER ON A MOVING CORE MEMBER BACKGROUND OF THE INVENTION The dip-forming process, such as used in continuous casting of metal, is now well known in the art. According to this process, an elongated body or core material such as a metal rod is typically pretreated by passing it through a straightener, a surface-cleaning apparatus and a shaving die which also serves as a vacuum seal for a vacuum entrance chamber positioned below or at the bottom of a crucible containing a bath of molten material. The continuous elongated core or body is passed upwardly through the molten bath, which bath may have the same chemical composition as that of the core or a different composition. The molten material in the crucible accretes or deposits upon the outer surface of the core thereby increasing its cross-sectional area appreciably. After emerging from the crucible the resulting casting member is cooled as by a water spray from one or more jet nozzles at least sufficiently so that the cast member may be rolled or worked. From there the cast member may be passed through a suitable roller mechanism where it is reduced in a cross-sectional area and then passed to a suitable receiving means such as a takeup reel.

The dip forming process briefly described above is fully set out in one or more of the following patents:

To the extent necessary the disclosures of the above-cited patents are incorporated by reference herein.

A metallurgical investigation led to our discovery that wire breaks occurring during the drawing of copper dip-formed rod are often caused by molybdenum inclusions. A study of the dip-forming process reveals that the only location in the system where molybdenum is known to be present is the bushing or nozzle in the entrance port. Thus we deducted that the molybdenum inclusions in the wire were the result of the use of a molybdenum bushing or nozzle through which the core material passed into the molten copper bath.

Two alternate causes of molybdenum inclusion in the copper rod appear to contribute to the problem. Mechanical removal of molybdenum particles from the bushing or nozzle may be due to spalling, welding, and/or galling. In combination with the mechanical removal, or by itself, there may be intergranular attack of molybdenum by molten copper and/or atmosphere in the molten metal crucible. It is theorized that the molybdenum particles embedded in the core material as it passes through the molybdenum bushing are those particles dislodged from the molybdenum bushing after the grain boundary is weakened by a combination of impurities and high temperatures. Certain impurities in the molten copper probably change the wetting characteristic at the molybdenum grain boundaries and the grain boundaries thus become weakened and particles of molybdenum become susceptible of mechanical removal by the core passing through the bushing. The fact that molybdenum is not insoluble in liquid copper may also contribute to the difficulty experienced.

Three patents cited above, US. Pat. Nos. 3,008,201; 3,235,960 and 3,466,l86, refer to the use of a refractory metal bushing or nozzle in the dip-forming system. In these cited patents the only refractory metal specifically named is molybdenum. Our investigation shows that two of the three refractory metals generally commercially available, i.e. molybdenum and tantalum, are not suitable for use in the dipforming system. The third commercially available refractory metal, tungsten, according to our investigation, finds marginal use in the dip-forming system. The third commercially available refractory metal, tungsten, according to our investigation, finds marginal use in the dip-forming system but is not as effective as other metals such as rhenium or rhenium-based alloys. Thus it is clear that the teaching in the cited patents cannot be relied upon by one skilled in the art.

SUMMARY AND OBJECTS The invention therefore relates to an apparatus for accreting molten material, i.e. copper, on a continuously moving rod wherein the rod passes through an entrance bushing whose physical characteristics are such that no material will be removed from the bushing and deposited on the moving rod to cause inclusions in the accreted rod or the wire products made therefrom. The chief object of the present invention is to provide an improved method and process for accreting molten material on a moving rod to form a rod having greater thickness and being substantially uniform in character and free of detrimental inclusions, welded particles, tears, scraps, gouges, and scratches experienced in the prior art process. Still another object of the invention is to provide an entrance bushing to the molten metal crucible having physical properties that will not result in mechanical removal of particles from the bushing due to spalling, galling, welding, and/or tearing.

DESCRIPTION OFTHE INVENTION The attached drawings illustrate a preferred embodiment of the invention.

FIG. I is a schematic flow diagram of the elements required to practice a method of accreting molten material on a moving member.

FIGS. 2A, 2B and 2C are sectional views ofa portion of the crucible illustrating the area through which the core member is introduced into the crucible and illustrating three types of bushings or nozzles.

As shown in FIG. 1, which is a schematic representation of the overall dip-forming process, an elongated body 1 of a length of material in the solid state having a first cross-sectional configuration and area is continuously withdrawn from a storage means 2 such as a reel or the like and is guided by an appropriate means such as a pulley 3 through preliminary treatment apparatus which may consist of a conventional straightener 4, a conventional surface-cleaning apparatus 5, for example an electrolytic bath, and a rinsing or washing bath 6. The straightened, cleaned and wet body 1 is guided by means 7 into and through an elongated or tubular conduit 8 comprising a drying means 9 which may be supplied with a neutral atmosphere from a source 10, conventional powerdriven feeder rolls 1] which frictionally engage and drive body 1 into a vacuum entrance chamber 12 provided with a vacuum source 13, which permits the body to pass therethrough while subject to vacuum but which prevents the passage of atmosphere therewith, and an entrance port I4 provided in the bottom of a crucible 15. The body I is then passed through a bath of molten material contained in crucible 15, the bath suitably but not necessarily having the same chemical composition as body 1.

Molten material in crucible 15 accretes or deposits and solidifies upon the outer surface of the body 1 increasing its cross-sectional area appreciably into a body 16 which may be of substantially homogeneous composition. After emerging from crucible 15, the body 16 may be subjected to water sprays from jet nozzles 29 and thereby cooled and then passed between sizing apparatus, such as a pair of sizing rolls 17 which function to remove or correct minor surface irregularities The body 16 is then guided by means of a cooling duct or conveyor 18 to any suitable receiving means such as a reel 19 where it may be allowed to accumulate. From the reel or receiving means 19 the body is passed through conventional reducing apparatus 20 such as wire-drawing apparatus or rolling equipment where the body 16 is reduced to a body I In operation, body 1 passes through the central aperture of element 50 and through the tubular member or element 54 and emerges in the bath of molten material contained in crucible 60. The internal dimensions and configurations of tubular Test material .\Iol vbdenum-50% rhenium embedded). This rhenium.

Soft rhenium.

llnrd rhenium. Tungsten.

Sintercd tungsten carbide.. Alumina A few scratches, dark material deposited on surafce (not A material contains molybdenum and Some tarnishing, no embedded rheninm- Several scratches, severe deformation,

no embedded rhenium nor tungsten Severely eroded, but no tantalum particles presenL Some tarnishing, no embedded tungsten nor cobalt Very little tarnishing, otherwise execlle nt surface.

having any desired reduced cross-sectional area. 5 member 54 are such that body 1 may freely pass therethrough Body 1 may be allowed to accumulate at a storage means but molten material may not leak downwardly along body I. 21 such as a reel or the like. When a sufficient length of body FIG. 2C illustrates yet another design for the entrance port I has accumulated in the storage means 21, body 1' may be to the molten metal crucible. Crucible liner 62 containing cut and the remainder of the body diverted to storage means molten metal 68 is enclosed in a crucible 6]. Tube 65, adapted 22 as product 23. Product 23, as indicated by arrow 24, may 10 to be evacuated, is connected to a vacuum source through be substantially continuously fed to other fabricating aptube 67. As rod 1 passes through the opening of tube 65 and is paratus or may be packaged at this point as a final product. introduced into nozzle 69 suitable clearance space 66 is pro- Theportion of the body 1' stored at 21 may be used to vided between rod 1 and the nozzle surface. At the discharge replenish body 1 in storage means 2 and permit continuous l 5 end 63 of nozzle 69 hydraulic pressure of the molten metal in operation of the apparatus. the crucible liner 62 combined with the vacuum in the open- Since body 1 is continuously passed through the crucible l5 ing brings the solidified material into the clearance 66. Conmolten material is continuously removed from the crucible. tinuous solidification of molten material at discharge end 63 The depth of the molten material in the crucible should be of the nozzle substantially prevents molten material flowing preferably maintained at a substantially constant depth and into nozzle to impede the successful operation of this continuthis may be continually accomplished by providing a melting S cr ti napparatus such as furnace 25. Material having the appropriate H ng discovered h maj r cause f r h wire r k g in composition is melted in furnace 25 and permitted to flow into pp wife made from the dip-formed Tod, the applicants h ibl h h a d i 26 a regulating valve 27 and a devised an accelerated test to determine the characteristics of heating launder or conduit 28 into the bath contained in the 25 materials that would meet the q of Spalhhgr crucible l5. galling, welding or tearing when a rod or core member was Referring now to HOS 2A 2B and 2C the.e is bw passed through a member made from the test materials at a ous designs of the entrance bushing or nozzle through which equal to or greater used m the I F' the core or wire rod passes into the molten metal bath. In FIG. g g A Sena? of smulated i fi t 2A there is shown a tube 30 defining an evacuated passage 0 y mmtmg. copperhsur ace 2 t c dcefo through which the core rod 1 passes into the crucible 31. test at 3 g t g z t Between the crucible 31 and the crucible liner 32 there is a coppehsu'r ace y h g out e nozzle 33 through which the core rod 1 passes into the molten i f zl g t F if w S 2"- bath 34. The nozzle 33 is a cylindrical member to be conmg ag i 27 Q e P gh f f structed from the materials as herein described. came usmg f lame er Copper V produced by the dip-forming process. A cross section of this 23 there Show nozzle and entrance P copper rod was polished and the rod was inserted in a drill emfance P compnses a centrally apenmied press. The candidate test materials were mounted in plastic cylindrical bushing element 50 of a thermally conductive and polished A 2O0 gram force was appncd between {he matenal h PP ha'vmg a flange 51 at one and and a copper wire rod and the candidate material surfaces. A drill reduced cylindrical extension 52 at its other end. The cenpress was rotated at about 3 00 f 10 mimmm r P aperture 3! the Outer end of emehsioh 52 is the test the two meeting surfaces, that is the surface of the tlrlgatideagrdlmegrzaglysfirzagidczsnzhglizpegtjgihg2113331152; cophper rod and the calnliiidate test materials}, were obscrvlcd wit a microscope. e copper r0 sur aces were a so descrlbed In this application is provided with a threaded collar analyzed by the electron microprobe f r h major l m 55 at about its midpoint and is threadedly secured to extension contained i the test m i r 52 with aportion of its length,formingaliner for extension 52 Th first test was i d out using molybdenum as test as shown. A substantially cylindrical bushing 56 of :1 Ceramic material. After the test, the molybdenum surface was severely material such as fired alumina or the like, is provided with a o d, and these grooves were partially filled with copper central aperture which receives extension 52 and that portion mixed with molybdenum particles. The copper surface was o tubular element 54 which extends beyon t e t rm n p severely roughened and several molybdenum inclusions were no;1 of CXIGIIStIOI'l A tzgttomhwarll of cru ibtll 6 ipt oii fi clearly visible. These inclusions were gositivcly lidentified by WI n aper ir W I W I 5 Secure a 5 an 18 y the electron microprobe as pure moly denum. his test concylindrical centrally apertured bushing 58 of a refractory firmed the earlier findings of molybdenum inclusion in the material such as graphite which retains within its aperture broken wire. ceramic bushing 56 as shown. Cooling means such as coil 59 Other tests were carried out using tantalum, tungsten. tungthrough which coolant may be circulated is in heat exchange sten 25 percent rhenium, molybdenum-50 percent rhenium, relationship with element 50 as shown and serves to extract soft rhenium, hard rhenium, alumina, and sintered tungsten heat from ele ent 50 and tub lar element 54- carbide as candidate materials with the following results:

TABLE I Condition ct- Copper surface Test material surface few scratches and a small amount of dark material deposited on surface.

- A fewseratehes, n0 embedded rhenium,somet-nrnishing. Surface scratched and deformed. No foreign material on surface.

. Excellent surface.

some tearing but Very few scratches. light stnin. otherwise excellent surface. Excellent surface. Copper welded to stlrfnee,

integrity. Excellent surface integrity. Excellent surface.

hut tantalum nrnintnined Alum TABLE. IITES'I MATERIALS Tungsten-25% Tungsten Molybdenum Tantalum Tungsten Rheniuni Molybdenum-50% rhenium alloy rhenium alloy carbide Soft"..- Sorta... 250 p.p.rn

Table 1] lists some known physical properties and observed characteristics of the test materials. As can be observed from a study of table ll the refractory metals, molybdenum and tantalum, would not be satisfactory 5 materials for construction of the nozzle or bushing.

Several observations can be made from table ll wit regard to the physical characteristics of materials from which entrance bushings or nozzles may be made. Relatively hard materials, i.e., tungsten, rhenium, and rhenium-based alloys should be 10 used to make the nozzles rather than the relatively soft refractory metalsmolybdenum and tantalum. Solubility of the nozzle construction material in molten copper should be less than approximately 250 p.p.m. Cold welding should not occur between the core rod and the bushing or nozzle construction material. The core rod surface should be relatively unaffected by its unavoidable contact with the interior walls of the bushing while moving at speeds of about 200 or more f.p.m.

From our tests and observations rhenium would be the most ideal material for the bushing. However it is relatively expensive. Alloying rhenium with molybdenum indicated that a suitable rhenium-molybdenum alloy for nozzle material contains at least 50 percent rhenium. Although tungsten along is a reasonably satisfactory bushing material it may be advantageously alloyed with rhenium. Any tungsten-rhenium alloy may be used within the scope of this invention. For economic considerations tungsten-rhenium alloys containing about 25 percent or less rhenium are preferred. It appears that tungsten carbide and alumina may be acceptable construction materials except that their well-known, low-impact resistance and thermal shock sensitivity may cause these materials to shatter in service.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. in an apparatus for the continuous casting of metals by running an elongated solid body into a molten copper bath at a point below the bath surface and running the body through the bath and into the space above the surface of the bath, which comprises a crucible having a molten metal bath-containing chamber, entrance chamber means providing an entrance chamber removed from the crucible bath-containing chamber, entrance port means disposed between the entrance chamber and the crucible bath-containing chamber and having a passageway connecting the bath-containing chamber and entrance chamber and opening into the bath-containing chamber below the normal molten metal bath surface level therein, the entrance port passage having a portion to cooperate with an elongated solid body passing through the entrance port means and providing a seal against a molten metal flow from the crucible bath-containing chamber to the entrance chamber, and means for running the elongated body through the entrance chamber and the entrance port means passageway and into and upwardly through the crucible bathcontaining chamber, the improvement wherein the entrance port means comprises a centrally apertured cylindrical bushing element having a flange at one end and a reduced cylindrical extension at its other end, a thin-wall tubular element having one end secured in the central apertured cylindrical bushing element, the other end of the tubular element extending beyond the reduced cylindrical extension of the bushing element, a first apertured bushing member enclosing the extended end of the tubular element and the reduced cylindrical extension of the bushing element, a second apertured bushing element which retains within its aperture the first apertured bushing; the thin-wall tubular element constructed from a material selected from rhenium, rheniumbased alloys, tungsten and tungsten-rhenium alloys.

2. In the apparatus of claim 1 wherein the entrance port means comprises a bushing made from a material selected from rhenium, a rhenium-molybdenum alloy containing at least 50 percent rhenium, tungsten, and a tungsten-rhenium alloy containing at least percent tungsten.

i p.p.n1 Unknown.. Unknown... Unkno\vn Unknown. No YoS Yes, 3 Material very hard and brittle, probably would shatter in service. 4 Wlodok, S. I., and Wulfi, J., Trans. AIME 218 (1960) 716.

. 1.400 p.p.m

. Yes......

' ziibtim'cijjljlL. 1 Visual and microscopic observation of surfaces of test materials and copper rod. 1 Best material but very expensive.

Relative hardness Solubility of test material in liquid copper Observed "001(1 welding Test material known to be prone to spalling Test rod surfaces 1 Test rod surfaces 1 contains test mater-i Test material useful as bushing mater-ML... 

1. In an apparatus for the continuous casting of metals by running an elongated solid body into a molten copper bath at a point below the bath surface and running the body through the bath and into the space above the surface of the bath, which comprises a crucible having a molten metal bath-containing chamber, entrance chamber means providing an entrance chamber removed from the crucible bath-containing chamber, entrance port means disposed between the entrance chamber and the crucible bath-containing chamber and having a passageway connecting the bath-containing chamber and entrance chamber and opening into the bath-containing chamber below the normal molten metal bath surface level therein, the entrance port passage having a portion to cooperate with an elongated solid body passing through the entrance port means and providing a seal against a molten metal flow from the crucible bath-containing chamber to the entrance chamber, and means for running the elongated body through the entrance chamber and the entrance port means passageway and into and upwardly through the crucible bath-containing chamber, the improvement wherein the entrance port means comprises a centrally apertured cylindrical bushing element having a flange at one end and a reduced cylindrical extension at its other end, a thin-wall tubular element having one end secured in the central apertured cylindrical bushing element, the other end of the tubular element extending beyond the reduced cylindrical extension of the bushing element, a first apertured bushing member enclosing the extended end of the tubular element and the reduced cylindrical extension of the bushing element, a second apertured bushing element which retains within its aperture the first apertured bushing; the thin-wall tubular element constructed from a material selected from rhenium, rhenium-based alloys, tungsten and tungsten-rhenium alloys.
 2. In the apparatus of claim 1 wherein the entrance port means comprises a bushing made from a material selected from rhenium, a rhenium-molybdenum alloy containing at least 50 percent rhenium, tungsten, and a tungsten-rhenium alloy containing at least 75 percent tungsten. 